1. Field of the Invention
The present invention relates to a semiconductor device and a position detecting method using the semiconductor device. In particular, the present invention relates to a position detecting method using the semiconductor device which detects a position by a radio signal from a plurality of interrogators.
2. Description of the Related Art
Nowadays, an individual information identification technology using wireless communication through an electromagnetic field, a radio wave, or the like has attracted attention. In particular, as a semiconductor device which communicates data by wireless communication, an individual information identification technology using an RFID (Radio Frequency Identification) has attracted attention. A semiconductor device including an RFID (hereinafter simply referred to as a semiconductor device) is also called an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technology using a semiconductor device has started to help production, management, or the like of an individual object and has been expected to be applied to personal authentication.
Semiconductor devices can be divided into two types: an active semiconductor device which can transmit a radio wave or an electromagnetic wave containing information on the semiconductor device and a passive semiconductor device which is driven using electric power of an external radio wave or electromagnetic wave (carrier wave), depending on whether it incorporates a power supply or it is supplied with electric power externally (as for an active type RFID, see Patent Document 1, and as for a passive type RFID, see Patent Document 2). An active semiconductor device incorporates a power supply for driving the semiconductor device and includes a cell as the power supply. A passive semiconductor device generates electric power for driving the semiconductor device by using electric power of an external radio wave or electromagnetic wave (carrier wave), and a structure where a cell is not provided is realized.
FIG. 14 is a block diagram showing a specific structure of an active semiconductor device. In an active semiconductor device 1400 of FIG. 14, a communication signal received by an antenna circuit 1401 is input to a demodulation circuit 1405 and an amplifier 1406 in a signal processing circuit 1402. Normally, the communication signal is transmitted after processing such as ASK modulation or PSK modulation is performed on a carrier of 13.56 MHz, 915 MHz, or the like. Here, FIG. 14 shows an example where 13.56 MHz is employed for the communication signal. In FIG. 14, a clock signal is necessary as a reference in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 1406 and then supplied to a logic circuit 1407 as a clock. Further, the communication signal which has been ASK modulated or PSK modulated is demodulated by the demodulation circuit 1405. The demodulated signal is also transmitted to the logic circuit 1407 and analyzed. The signal analyzed by the logic circuit 1407 is transmitted to a memory control circuit 1408, and based on the signal, the memory control circuit 1408 controls a memory circuit 1409, retrieves data stored in the memory circuit 1409, and transmits it to a logic circuit 1410. The signal is encoded by the logic circuit 1410, and subsequently amplified by an amplifier 1411. In accordance with the signal, a modulation circuit 1412 modulates the carrier. A power supply in FIG. 14 is supplied by a cell 1403 provided outside the signal processing circuit 1402 through a power supply circuit 1404. The power supply circuit 1404 supplies electric power to the amplifier 1406, the demodulation circuit 1405, the logic circuit 1407, the memory control circuit 1408, the memory circuit 1409, the logic circuit 1410, the amplifier 1411, the modulation circuit 1412, and the like. In this manner, the active semiconductor device operates.
FIG. 15 is a block diagram showing a specific structure of a passive semiconductor device. In a passive semiconductor device 1500 of FIG. 15, a communication signal received by an antenna circuit 1501 is input to a demodulation circuit 1505 and an amplifier 1506 in a signal processing circuit 1502. Normally, the communication signal is transmitted after processing such as ASK modulation or PSK modulation is performed on a carrier of 13.56 MHz, 915 MHz, or the like. FIG. 15 shows an example where 13.56 MHz is used for the communication signal. In FIG. 15, a clock signal is necessary as a reference in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 1506 and then supplied to a logic circuit 1507 as a clock. Further, the communication signal which has been ASK modulated or PSK modulated is demodulated by the demodulation circuit 1505. The demodulated signal is also transmitted to the logic circuit 1507 and analyzed. The signal analyzed by the logic circuit 1507 is transmitted to a memory control circuit 1508, and based on the signal, the memory control circuit 1508 controls a memory circuit 1509, retrieves data stored in the memory circuit 1509, and transmits it to a logic circuit 1510. The signal is encoded by the logic circuit 1510, and subsequently amplified by an amplifier 1511. In accordance with the signal, a modulation circuit 1512 modulates the carrier. On the other hand, the communication signal transmitted to a rectifier circuit 1503 is rectified and then input to a power supply circuit 1504. The power supply circuit 1504 supplies electric power to the amplifier 1506, the demodulation circuit 1505, the logic circuit 1507, the memory control circuit 1508, the memory circuit 1509, the logic circuit 1510, the amplifier 1511, the modulation circuit 1512, and the like. In this manner, the passive semiconductor device operates.
[Patent Document 1]
Japanese Published Patent Publication No. 2005-316724
[Patent Document 2]
Japanese Translation of PCT International Application No. 2006-503376